JP6994277B1 - Manufacturing method of injection molded products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently manufacture an injection molded product. SOLUTION: The mold surface forming sheet 30 is made of a flat plate-shaped elastomer sheet and has a first surface 31 and a second surface 32, and a pattern M due to unevenness of the elastomer itself is formed on the first surface 31. A sheet preparation step for preparing the formed mold surface forming sheet 30 and an injection molding mold 40 having a concave inner surface 42A, the second surface 32 is directed toward the inner surface 42A of the mold, and the first surface 31 The sheet fixing step of fixing the mold surface forming sheet 30 and the mold clamping step of molding the mold 40 with the mold 40 facing into the cavity, and the molten resin MP pressure by injecting the molten resin into the cavity. The mold surface forming sheet 30 is deformed by the above method, the second surface 32 is pressed against the inner surface 42A of the mold 40, and the pattern of the first surface 31 is transferred to the product surface PS of the molten resin MP, and the molten resin. After the MP is solidified, the injection-molded product 50 is taken out with the mold surface forming sheet 30 left in the mold 40. [Selection diagram] FIG. 4

Description

The present invention relates to a method for molding an injection-molded article having a pattern formed on its surface.

Conventionally, a mold surface forming sheet is created by screen printing a pattern consisting of fine lines with a fine line pitch on the surface of a resin film, and this mold surface forming sheet is placed in a mold and injected. An invention of transferring a pattern to the surface of a molded product is known. This makes it possible to easily manufacture an injection-molded product having a pattern on the surface without directly forming a pattern on the surface of the mold.

Japanese Patent No. 5750747

However, since the conventional mold surface forming sheet has a pattern formed by printing, there is a problem that the pattern is easily damaged when injection molding is repeated. In addition, the conventional mold surface forming sheet is thermally deformed along the inner surface of the mold due to heat during injection molding, and remains in the mold so as to stick to the inner surface of the mold, and is the boundary between the cavity and the parting line. Strong creases are formed where there is a change in shape such as. Further, since the resin film is not flexible, there is a problem that it is easily cracked from this strong crease portion.

Therefore, an object of the present invention is to provide a method for efficiently manufacturing an injection-molded product by reducing the frequency of replacing the mold surface forming sheet.

A method for manufacturing an injection-molded article to achieve the above-mentioned object is a mold surface forming sheet made of a flat plate-shaped elastomer sheet and having a first surface and a second surface opposite to the first surface. Therefore, a sheet preparation step for preparing a mold surface forming sheet in which a pattern formed by the unevenness of the elastomer itself is formed on the first surface, and an injection molding mold having a concave inner surface, the second surface is a mold. A sheet fixing step for fixing the mold surface forming sheet, a mold clamping step for molding the mold, and a molten resin injected into the cavity with the first surface facing the inner surface of the mold and the first surface facing the inside of the cavity. The molding process of deforming the mold surface forming sheet by the pressure of the molten resin, pressing the second surface against the inner surface of the mold, and transferring the pattern of the first surface to the product surface of the molten resin, and the molten resin After solidification, it has a take-out step of taking out an injection-molded product with the mold surface forming sheet left in the mold.

According to such a configuration, since the elastomer mold surface forming sheet is in the shape of a flat plate, it is possible to easily create a pattern due to unevenness. Since the mold surface forming sheet is a flat plate-shaped elastomer sheet, it is more flexible and less likely to be damaged than the conventional resin film. Further, since the pattern on the first surface of the mold surface forming sheet is formed not by the printing ink but by the unevenness of the elastomer itself, it can be used for repeated injection molding as compared with the case of printing, that is, the unevenness caused by the ink. On the other hand, it is highly durable. Therefore, the frequency of replacing the mold surface forming sheet can be reduced, and the injection molded product can be efficiently manufactured.

In the taking-out step described above, the mold surface forming sheet may be elastically returned to a flat plate shape.

That is, by using an elastomer mold surface forming sheet having sufficient heat resistance, the mold surface forming sheet returns to a flat plate shape when the mold is opened in the extraction process, and at this time, the injection molded product is extruded. Therefore, the injection-molded product can be taken out smoothly.

In the sheet preparation step described above, a pattern raised by printing is formed on the surface of a flat metal plate to create an original plate, and the elastomer material is brought into close contact with the surface of the original plate on which the pattern is formed to form an elastomer. After curing, the cured elastomer can be peeled off from the original plate to prepare a mold surface forming sheet.

According to such a method, a pattern can be easily formed on a metal plate by printing, and the pattern can be easily transferred to the elastomer to form a pattern due to unevenness on the elastomer.

In the above-mentioned sheet preparation step, the surface of the flat plate-shaped elastomer sheet may be formed into irregularities by laser engraving to prepare a mold surface forming sheet.

According to such a configuration, a pattern due to unevenness can be easily formed on the elastomer.

According to the present invention, it is possible to efficiently manufacture an injection-molded product by reducing the frequency of replacing the mold surface forming sheet.

It is a front view (a) of the injection-molded article by the manufacturing method of this invention, and is the enlarged view of the pattern part of (a). It is the front view (a) of the original plate which the pattern was formed by printing, and the partially enlarged sectional view of (a). It is a figure (a) in which the original plate is arranged in a mold, and the figure (b) at the time of molding a mold surface forming sheet. It is a figure explaining the process of injection molding, (a) a fixing process which fixes a mold surface forming sheet, (b) a mold clamping process which fixes a mold surface forming sheet to a mold, and (b). c) The molding process of injecting the molten resin and (d) the taking-out process of opening the mold and taking out the injection-molded product are shown.

Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1A, the injection-molded article 50 manufactured by the manufacturing method of the present invention has a pattern M formed on the surface thereof due to unevenness. In the injection molded product 50, the surface having the pattern M is raised in a curved shape, and the back side is recessed. The lines constituting the pattern M are formed by extending a long protruding shape like a ridge.

As shown in an enlarged view of a part of the pattern M in FIG. 1 (b), the pattern M has fine hatching 3A, 3B, 3C in addition to the line 2 indicating the boundary of the region. Each hatch 3A, 3B, 3C is composed of parallel lines, and the direction in which the hatch 3A extends, the direction in which the hatch 3B extends, and the direction in which the hatch 3C extends are different from each other. Therefore, among the hatches 3A, 3B, and 3C, there are those that strongly reflect light and those that reflect light weakly, depending on the direction in which the person views the pattern M. Therefore, the pattern M gives a glittering impression because the emphasized and visible portion differs depending on the viewing direction of the person.

In the manufacturing method of the present embodiment, first, a mold surface forming sheet 30 (see FIG. 3C) in which a pattern M due to unevenness is formed on the surface of the elastomer is prepared (sheet preparation step).

In the sheet preparation step, as shown in FIGS. 2A and 2B, a pattern M raised by printing is formed on the surface of the flat metal plate 11, and the original plate 10 is created. For printing in this case, a screen printing or inkjet printing method can be used. The ink used for printing is an ultraviolet curable ink, and by applying the ink on the surface of the metal plate 11 and then applying ultraviolet rays, it is possible to quickly perform heap printing. Alternatively, so-called barco printing may be used in which ordinary ink is used and the resin powder is applied to the ink before the ink dries to melt and fix the resin powder.

The material of the metal plate 11 is not particularly limited as long as the ink can be fixed, but for example, aluminum or stainless steel can be used. By using the metal plate 11 as the material of the original plate 11, the molded elastomer mold surface forming sheet 30 can be easily peeled off from the original plate 10.

Then, as shown in FIGS. 3 (a) to 3 (c), the original plate 10 is used to prepare the elastomer mold surface forming sheet 30.
To prepare the mold surface forming sheet 30, for example, as shown in FIG. 3A, the original plate 10 is installed on the inner surface of the mold 20 having a dent slightly deeper than the thickness of the original plate 10. The mold 20 has a fixed mold 22 and a movable mold 21, and the original plate 10 is installed on the inner surface of either mold so that the pattern M faces the cavity (inside the space of the mold). At this time, by installing the pin P, the hole 35 can be formed in the molded mold surface forming sheet 30.

Then, as shown in FIG. 3B, by injecting the elastomer material EM, the elastomer material EM is brought into close contact with the surface of the original plate 10 on which the pattern M is formed. The material EM of the elastomer is not particularly limited, but either a thermoplastic material or a thermosetting material can be used. Examples of the thermoplastic elastomer material include styrene-based, olefin-based, ester-based, hard vinyl chloride-based, urethane-based, and amide-based materials. Further, in the case of a thermosetting material, a silicone elastomer can be used in addition to a butadiene-based material, an isoprene-based material, and a urethane-based material. It is particularly desirable to use a silicone elastomer having excellent heat resistance and flexibility for the mold surface forming sheet 30. Regardless of which material is used, it is desirable that the elastomer has high heat resistance, and at least a heat resistant material that can withstand the melting point of the resin used in the molding step described later is used.

Then, as shown in FIG. 3C, after the elastomer is cured, the cured elastomer is peeled off from the original plate 10 to prepare a mold surface forming sheet 30. The mold surface forming sheet 30 is made of a flat plate-shaped elastomer sheet, and has a first surface 31 and a second surface 32 opposite to the first surface 31. The convex shape of the ink 13 is inverted and transferred to the first surface 31 of the mold surface creating sheet, so that the pattern M is formed by the unevenness of the elastomer itself. In the present embodiment, the pattern M is formed by the recess 33 to which the convex shape of the ink 13 is transferred. When the pin P is installed in the mold 20, the hole 35 corresponding to the pin P is formed in the mold surface forming sheet 30.

After preparing the mold surface forming sheet 30, as shown in FIG. 4A, the second surface 32 is directed toward the inner surface 42A of the mold 40 toward the injection molding mold 40 having the concave inner surface 42A. The mold surface forming sheet 30 is fixed with the first surface 31 facing into the cavity (sheet fixing step).

Specifically, the mold 40 has, as an example, a fixed mold 41 and a movable mold 42, and the movable mold 42 has a recessed inner surface 42A. The fixed mold 41 has a convex inner surface 41A corresponding to the concave inner surface 42A. Either the fixed type 41 or the movable type 42 may have the concave inner surface 42A. The movable mold 42 may have a pin P2 for fixing the mold surface forming sheet 30 by engaging the hole 35 of the mold surface forming sheet 30. When the mold surface forming sheet 30 is fixed to the mold 40, it may be fixed to the outer flat surface portion 44 of the concave inner surface 42A. When fixing the mold surface forming sheet 30 to the mold 40, an adhesive or double-sided tape may be used. In the state where the mold surface forming sheet 30 is fixed to the mold 40, the mold surface forming sheet 30 has a flat plate shape, and therefore, simply fixed to the movable mold 42 does not adhere to the concave inner surface 42A (two points). See chain line).

As shown in FIG. 4B, when the mold 40 is molded (molding step), the mold surface forming sheet 30 is pushed by the convex inner surface 41A and stretches, but the concave inner surface 42A Does not stick. In the mold 40, the cavity in which the material is filled is a space between the mold surface forming sheet 30 and the convex inner surface 41A (a space in which the molten resin MP is filled in the next molding step).

Next, as shown in FIG. 4C, the molten resin MP is injected into the cavity, the mold surface forming sheet 30 is deformed by the pressure of the molten resin MP, and the second surface 32 is formed on the mold 40. While pressing against the inner surface 42A, the pattern M on the first surface 31 is transferred to the product surface PS of the molten resin MP (molding step).

Then, as shown in FIG. 4D, after the molten resin MP is solidified, the injection-molded product 50 is taken out with the mold surface forming sheet 30 left in the mold 40 (take-out step). If the runner 59 or the like remains in the injection molded product 50, the runner 59 is cut off. The uneven shape of the first surface 31 of the mold surface forming sheet 30 is transferred to the surface of the injection molded product 50 to form a pattern M. In the present embodiment, the pattern M is a pattern having a convex shape 53.

When the mold surface forming sheet 30 is a material having excellent heat resistance, the mold surface forming sheet 30 returns to a flat plate shape due to its elasticity in the taking-out step. Therefore, the injection molded product 50 can be smoothly peeled off from the mold surface forming sheet 30 and taken out by utilizing the force of the mold surface forming sheet 30 to return to a flat plate shape. As in the case of normal injection molding, it is desirable to appropriately use an extrusion pin for extraction.

According to the method for manufacturing an injection-molded article of the present embodiment described above, the following effects can be obtained.
Since the elastomer of the mold surface forming sheet 30 has a flat plate shape, it is possible to easily create a pattern due to unevenness. In the present embodiment, the convex shape formed by printing is transferred at the time of molding the elastomer, so that the concave shape 33 of the elastomer itself can be easily formed on the surface of the elastomer. Since the convex shape formed by this printing is formed on the surface of the flat metal plate 11, it can be easily created.

Since the mold surface forming sheet 30 is a flat plate-shaped elastomer sheet, it is more flexible than the conventional resin film, is less likely to be creases, and is less likely to be damaged. Further, since the pattern M on the first surface 31 of the mold surface forming sheet 30 is formed not by the ink for printing but by the unevenness of the elastomer itself, it can be subjected to repeated injection molding as compared with the case of unevenness due to printing. And highly durable. Therefore, the frequency of replacement of the mold surface forming sheet 30 can be reduced, and the injection molded product 50 can be efficiently manufactured.

Further, when the mold 40 is opened in the taking-out step, the mold surface forming sheet 30 returns to a flat plate shape, and at this time, the injection-molded product 50 is extruded, so that the injection-molded product 50 can be taken out smoothly.

Further, in the present embodiment, the pattern M is easily formed on the metal plate 11 by printing, and the pattern M is transferred to the elastomer to easily form the pattern M due to the unevenness on the mold surface forming sheet 30. be able to.

Although one embodiment of the present invention has been described above, the present invention can be appropriately modified and implemented without being limited to the above-described embodiment.
For example, in the above embodiment, the unevenness formed by printing on the metal plate 11 is transferred to the elastomer to form the unevenness on the surface of the elastomer, but in the sheet preparation step, the laser is applied to the surface of the flat elastomer sheet. A sheet for forming a mold surface may be created by forming irregularities by engraving.
Even by such a method, a pattern due to unevenness can be easily formed on the elastomer.

Further, in the above embodiment, the original plate is created by forming unevenness on the metal plate by printing, but the unevenness may be formed on the surface of the metal plate by laser engraving, machining, or processing by a craftsman. .. Such irregularities other than printing may be transferred to the surface of the elastomer. Further, the material of the original plate is not limited to a metal plate as long as it can be used for molding an elastomer, and may be, for example, ceramic or the like.
Further, the mold surface creation sheet may be created by another person without creating it by oneself.

In the above embodiment, the pattern is drawn on the surface of the elastomer with lines having a concave shape, but a pattern may be drawn with lines or dots having a convex shape. For example, if a concave pattern is formed on the surface of a metal plate by laser engraving and this pattern is transferred to the surface of the elastomer, a convex pattern can be formed on the surface of the elastomer. Further, both the concave line and the convex line may be formed on the surface of the elastomer.

Further, the pattern may be a changing image consisting of fine lines as described in Japanese Patent No. 5594641. The changing image is provided in a range overlapping with the first line drawing forming the background base pattern and the first line drawing by a plurality of parallel broken lines, and is parallel to the direction different from the broken line of the first line drawing. It has at least one second line drawing that constitutes a pattern by a plurality of broken lines. Each broken line is composed of ridge-shaped ridges, so that the visible pattern changes depending on the viewing direction. Since such a line drawing with fine lines is suitable for a method of forming unevenness by printing, the present invention can be effectively used.

Further, each element described in the above-described embodiment and modification may be arbitrarily combined and carried out.

10 Original plate 11 Metal plate 13 Ink 20 Mold 30 Mold surface forming sheet 31 1st surface 32 2nd surface 33 Concave shape 40 Mold 42A Inner surface 50 Injection molded product

Claims (5)

It is a manufacturing method of injection molded products.
A mold surface forming sheet made of a flat plate-shaped elastomer sheet and having a first surface and a second surface opposite to the first surface, and a pattern on the first surface due to the unevenness of the elastomer itself. The sheet preparation process for preparing the mold surface forming sheet on which the
The mold surface forming sheet is fixed to a mold for injection molding having a concave inner surface with the second surface facing the inner surface of the mold and the first surface facing the cavity. Sheet fixing process and
The mold clamping process for molding the mold and
The molten resin is injected into the cavity, the mold surface forming sheet is deformed by the pressure of the molten resin, the second surface is pressed against the inner surface of the mold, and the pattern of the first surface is formed. The molding process of transferring the molten resin to the product surface and
A method for manufacturing an injection-molded product, which comprises a step of taking out an injection-molded product with the mold surface forming sheet left in the mold after the molten resin is solidified. The method for manufacturing an injection-molded article according to claim 1, wherein in the taking-out step, the mold surface forming sheet returns to a flat plate shape due to elasticity. In the sheet preparation process
An original plate is created by forming a raised pattern by printing on the surface of a flat metal plate.
The elastomer material is brought into close contact with the surface of the original plate on which the pattern is formed.
The method for producing an injection-molded article according to claim 1 or 2, wherein after the elastomer is cured, the cured elastomer is peeled off from the original plate to produce the mold surface forming sheet. The injection molding according to claim 1 or 2, wherein in the sheet preparation step, unevenness is formed on the surface of a flat plate-shaped elastomer sheet by laser engraving to prepare the mold surface forming sheet. Manufacturing method of the product. The method for producing an injection-molded article according to any one of claims 1 to 4, wherein the elastomer is a silicone elastomer.

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